


The Substitute

by thegreymoon



Series: Kinkalot 2019 [5]
Category: Merlin (TV)
Genre: Alternate Universe - Canon Divergence, Angst with a Happy Ending, Fuck Or Die, Healing Sex, M/M, Magic Made Them Do It, Magical Healing Cock, Minor Gwen/Arthur Pendragon (Merlin), Mordred Needs To Die, One-Sided Mordred/Arthur Pendragon (Merlin) - Freeform, Soul Bond
Language: English
Status: Completed
Published: 2019-09-12
Updated: 2019-09-12
Packaged: 2020-10-17 03:43:47
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,000
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20614415
Author URL: https://archiveofourown.org/users/thegreymoon/pseuds/thegreymoon
Summary: Mordred isn't the only one who wants things he cannot have.





	The Substitute

**Author's Note:**

> Written for [Kinkalot's](https://kinkalot.livejournal.com/) [Challenge 4: Magic Made Them Do It!](https://kinkalot.livejournal.com/7367.html)

Merlin took Arthur’s face into his hands and despaired at the web of black, protruding vessels that branched up his neck. The dark magic was spreading. He would personally kill Mordred when he found him again, like he should have done long ago, before he was given the chance to do… this.

“Why? Why did you let him escape?”

Arthur smiled, but it was pained.

“Shh, my mouse,” he soothed, but his voice was hollow and rasping, as if it was already coming from the spirit world. “There was no point in keeping him. Don’t weep. I could never bear your tears.”

“No! I don’t accept this! I refuse! There must be something!”

“There is nothing,” Arthur coughed up black smoke. His eyes were bloodshot, his lips purple, and black blood trickled from the corner of his mouth. “Just… Just stay with me.”

Sobbing, Merlin straddled him, holding his head to his chest. Arthur’s weak arms closed around his waist.

“I’ve always wanted to die in your arms.”

“Don’t say that,” Merlin begged, tears falling freely into Arthur’s hair. It used to be so golden, but was now brittle and dull. “Stay with me. Don’t leave me, not now, not when…”

“You should have told me, Merlin.”

“I didn’t want to make you choose.”

“You must know,” Arthur whispered. “You must know I would have always chosen you!”

“Why? Why didn’t you do what he wanted?” Merlin wailed. “If it wasn’t the magic that stopped you, then what?”

“I already bound myself to the wrong person once. I would not do it again, especially not in an eternal bond that can never be broken. Not to him. Never to him.”

“But you liked him!”

Arthur shrugged.

“Maybe once. Not anymore.”

“But you’ll die!”

“Then I choose death.”

Merlin keened as if wounded and Arthur pulled back to stroke his cheek.

“Come now,” he said. “You always hated him. Could you really stand to see him by my side?”

“I’d stand anything not to lose you!” Merlin sobbed and lunged forward, kissing him fully on his blackened mouth.

Shocked, Arthur pushed him away.

“No, Merlin,” he gasped, “Don’t! Not if you don’t mean it! Not now!”

“I love you,” Merlin choked. “I have, for years!”

He kissed him again, and this time, Arthur didn’t push him off. He kissed back, hungry and desperate, as if Merlin’s breath was the last air he would ever get to breathe. He felt Merlin’s magic spill into him. The darkness inside sizzled and hissed, then it latched on, because it fed on the lust. The spell demanded it, starved and needy after it had already been denied. Merlin could see it clearly now, the threads of corruption wrapping like a disease around Arthur’s bright core, the net Mordred had been weaving since the first day he’d walked back into Arthur’s life. It had grown like a tumour around Arthur’s mighty life force, feeding off it, and filled despair, Merlin reached in and grasped one of the larger coils, like he would seize a rabid animal by the throat. He choked and burned it with all the hatred he could muster, and to his surprise, it writhed as if in pain, then shrieked and dissolved. Arthur gasped in relief, and the core of him shone a little brighter, the light of him escaping from the sticky, toxic web. The other threads trembled and sputtered as Merlin reached for another, then another, then another. There were dozens, there were hundreds, but Merlin didn’t care. He would kill them all, one by one, until Arthur was released. His own essence suffused Arthur’s blood, burning out the blackness until only magic fire was left in its wake. The bond sealed as they ground against each other, expelling the poison piece by piece.

-

They lay together afterwards, covered in sweat and come.

“How?” Merlin whispered. “The spell doesn’t allow a substitute.”

“Substitute?” Arthur asked, his brain slow to catch up. He was still breathing heavily, healthy and golden once more, his chest rising and falling under Merlin’s weight.

“The spell feeds on genuine want,” Merlin said. “It is linked to the object of your lust. You must bind or die. Only Mordred could break it!”

“Oh,” Arthur said and something in his tone caught Merlin’s attention. He looked up, his eyes still red, his lips swollen. Arthur had never seen him so beautiful. “You’re an idiot.”

“Me? What do you mean?”

Arthur reached up and stroked his tear-streaked face.

“It’s you,” he said. “It has only ever been you. Mordred was the substitute.” 

Merlin blinked, uncomprehending.

“He has the same energy,” Arthur explained. “Morgana used to have it too, before she… became what she is. Now I know it’s only kindred magic.”

“Oh,” Merlin didn’t know how to process this.

“You were so distant. You no longer talked to me or smiled for me. It was as if every day you spent at my side was a burden and when he looked at me like I was the centre of his world, it was like an echo of you, of how you were when you first came to Camelot, before I… before I married her, and you pulled away. Having him close made missing you easier and sometimes, I allowed myself to pretend. That’s what he took advantage of. That was the seed of his enchantment.”

Merlin smacked him.

“And you knew?” he cried. “You knew and you didn’t tell me? You could have died! I could have lost you and you didn’t say!”

Arthur looked guilty.

“What right did I have?” he said. “If you don’t want me, it is meaningless. I’d rather be dead than shackle you out of duty. If I’d known... When I married, if I’d understood then what I was losing, I would never have done it.”

Merlin stared at him, kissed him, and then stared again, marvelling.

“You’re such a fool,” he said. “I was born to love you. You can never lose me.”

**Author's Note:**

> Too much unnecessary sadness! I continue failing at porn at a porn fest and the only thing I can offer in my defence is the Canon Divergence! Yay! Merthur gets to avoid that heart-rending finale and they live happily ever after! Also, Mordred gets swallowed by sentient quicksand offscreen before he can come back to cause more trouble and I'm not accepting alternative opinions on this.


End file.
